Inadequate bone volume is a well recognized problem in the craniofacial and orthopedic fields. For example, ordinarily, a dental implant must be fit into an implant bed within existing bone and corresponding in shape to the implant. Standard implants have a cylindrical or slightly tapered shape in order to allow for a path of placement into bone with the close adaptation needed for stability and to encourage the selective re-population of the implant site with osteogenic potential cells versus being encapsulated within fibrous tissue. In a large proportion of clinical cases, there is inadequate bone height and/or width for the placement of standard endosseous dental implants.
Dental implants to replace missing teeth are 90-95% successful in clinical practice, when placed under optimal conditions. These conditions include good systemic health of the patient and acceptable bone quality, acceptable bone volume and acceptable bone shape at the implant site. Unfortunately, bone resorbs after tooth loss. Due to this continued bone loss, a substantial segment of the population has insufficient bone volume to benefit from implant placement. Bone grafting is currently the standard method for increasing the height and width of the bone ridge, and thereby maxillofacial bone volume. Current bone graft methods include painful, invasive and sometimes hazardous or prolonged procedures generally requiring an extensive donor site at locations such as the rib, hip or leg bone or blocks of bone from the jaw.
Tissue engineering methods to augment bone volume, in edentulous regions where standard implant placement is not possible, are under intense development. These methods involve the use of scaffolds, growth factors and cells with osteogenic potential. However, at present there are significant limitations to the dimensions (especially thickness) of material that can be implanted due to issues involving extra-cellular transport of metabolites and products; the lifetime and effective diffusion distance and presentation timing of signaling moieties; and the multitude of support functions provided by a properly distributed vasculature. Thus, for example, many tissue-engineered products are limited to thicknesses of two to three millimeters, likely an inadequate dimension to be clinically meaningful in one surgical step.